1. Field of the Invention
The present invention relates to a novel recording liquid which provides high density images having excellent waterfastness and high quality for recording on sheets of paper normally used in offices or schools. The present invention also relates to an ink jet recording method of the type in which such a recording liquid is ejected for recording by the action of thermal energy.
2. Description of the Related Art
Various types of compositions have been proposed as inks for use in recording images on a material, such as a sheet of paper. Such inks may be used in conjunction with writing implements, stamps, recorders or ink jet recording devices. Typical inks are composed of various types of dyes and water or other organic solvents in which the dyes are dissolved or dispersed.
Various types of ink jet recording methods are known. Typical examples include: an ink jet recording method in which a portion of the charged droplets which are generated in sequence are used for recording; an ink jet recording method in which a signal is supplied to a recording head incorporating a piezoelectric element so that a droplet of a recording liquid can be generated in response to the signal supplied for recording; and an ink jet recording method in which thermal energy is applied to a recording liquid contained in a chamber of a recording head in accordance with a recording signal so as to generate a droplet. Owing to their peculiarity, such ink jet recording methods require a recording liquid which satisfies stricter conditions as compared with those recording liquids used in conjunction with the writing implements, stamps or recorders.
Those conditions include:
(1) A recording liquid which allows vivid images having a contrast to be recorded at a high density.
(2) A recording liquid which allows high-quality images to be recorded on any type of recording medium without irregular blurring.
(3) A recording liquid which can be fixed to a recording medium quickly (e.g., can be dried quickly on a recording medium) and firmly, and cannot therefore be scrubbed off.
(4) A recording liquid which ensures that the printed images exhibit excellent waterfastness and lightfastness.
(5) A recording liquid which can be ejected from a fine orifice stably in the form of droplets without clogging the orifice.
(6) Even when kept uncapped while the recording is being suspended, a recording liquid is provided which can be ejected stably immediately after recording has been restarted. In other words, ink located near the orifice is not readily dried, thus preventing clogging.
(7) A recording liquid which can be stored stably for a long period of time without deterioration in the ink performance.
(8) A recording liquid which does not corrode the member with which it is in contact.
(9) A recording liquid which is safe, non-toxic and not flammable.
In order to fulfill all the conditions described above, various ink jet components have been proposed. However, none of them fulfills all the above conditions. Recording liquids which contain a certain type of disazo dye, a certain type of trisazo dye or a combination of these dyes have been proposed in the specifications of, for example, U.S. Pat. Nos. 4,724,001, 4,765,838 and Japanese Patent Laid-Open No. 285275/1986. These recording liquids exhibit excellent thermal stability and excellent waterfastness, can be stored stably for a long time without degradation in the quality, and are capable of preventing clogging as compared to a recording liquid which contains a conventionally employed dye.
U.S. Pat. No. 4,601,756 discloses an improved black color ink which contains both C.I. Food Black 2 and dyes having other color tones.
Although the above-described recording liquids exhibit the aforementioned various characteristics, they do not provide images having both excellent waterfastness and high density.